Leon Abeyta

1
EVLA LO/IF

• Central and Antenna
• Reference Generation

2
Reference Gen

• GOALS
• Frequency Multipliers and Dividers Phase Noise
• - Design as close to 20log(f1/f0) as
  possible
• Frequency Generators Spurious
• - Harmonically related gt25 dBc
• - Non-harmonically related gt40 dBc
• Low peak-to-peak phase deviations

3
Reference Gen

• Components Being Considered
• Frequency Dividers
• Wenzel LNFDs Low Phase Noise
• - 50 ohm devices
• - Internal BPFs
• ECL - Low Propagation
  Delays
• - Delays
  insensitive to Supply
• Variations
• - Less sensitive
  to temp than CMOS/TTL

4
Reference Gen

• Components Being Considered
• Frequency Multipliers COTS

5
Central Ref System

• REQUIREMENTS
• Generate and Distribute all references required
• Provide adequate spare freq ports and monitors
• Provide amplitude comp as needed
• Spare master gen to be continuously checked by
• comparison to primary

6
Central Ref System

• References provided by Frequency Standard
• 5 MHz -Will be used to generate 128
  MHz
• 100 MHZ -Available, if necessary for PCAL
• References provided by GPS
• 1PPS - To synchronize all EVLA Clocks to
• UTC
• - To monitor time drift

7
Central Ref System

• References generated
• 128 MHz Generated from maser 5 MHz and
• used to generate all other references.
  Clock for
• the Transition Converter.
• 256 MHz Clock for the IF Data
  Deformatters
• 512 MHz Sent to the Offset Gen and
  transmitted
• to the antennas
• 32 MHz - Modulated with Timing Signals
  and then
• transmitted to the antennas
  

8
Central Ref System

• References generated
• 128 Hz Sent to Master Offset Generator
  and Round Trip
• Phase Receivers
• 19.2 Hz Timing for Transition Period
• N x10mSec Timing when new hardware is on
  line

9
Central Ref System

• Critical Units
• 128 MHz Gen PLL Synth with loop BW set to
• take advantage of maser and VCXO phase noise
• 19.2 Hz Gen DDS
• 128 Hz Gen PLD
• Timing Modulator
• Nx10mSec Generator

10
Antenna Ref System

• REQUIREMENTS
• Receive, generate, and distribute references
• Provide amplitude and phase comp as needed
• Generate a PCAL comb
• Monitor phase of 4.096 GHz vs 128 MHz
• Demodulate Timing Signals

11
Antenna Ref System

• References Received
• 512 MHz Cleaned up for RTP and gen of
  other antenna
• frequencies
• 100 MHz Reference for PCAL Generator
• 32 MHz - Modulated with timing signals

12
Antenna Ref System

• References Generated
• 256 MHz Clock for FTS in 1rst and 2nd LO
  Synths, Ref
• for sampler modules and
  DTS modules
• 128 MHz Comb Ref for 2nd LO Synth
• 512 MHz Comb Ref for 1rst LO Synth
• 1.024 GHz - Ref for 4/P to L-Band
  Converter

13
Antenna Ref System

• References Generated
• 2.048 GHz Clock for LB Sampler Modules
• 4.096 GHz Clock for HB Sampler Modules
• 19.2 Hz Timing for Transition Period
• Nx10mSec Timing when new hardware is on
  line

14
Antenna Ref System

• PCAL Generator
• VLBA Compatibility
• Used on 3 Antennas
• Will require 5 or 100 MHz sent to antennas
• VLBA Tunnel Diode is now obsolete